From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Blueprint of a 'Birmann' impeller for high-speed superchargers.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan056 | |
| Date | 1st December 1930 | |
| "BIRMANN" IMPELLER FOR SUPERCHARGERS FOR HIGH SPEED BACKFEED BLADES STRAIGHT CONICAL EDGES TO BLADES. ALTERNATE BLADES CUT AWAY AT ROOT TO GIVE FREE ENTRANCE TO GAS. WCH Dec 1930 | ||